GNFAC Avalanche Forecast for Sun Apr 8, 2018

Not the Current Forecast

Good Morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Advisory issued on Sunday, April 8th at 7:00 a.m. This is our 136th and last daily advisory of the season. This advisory is dedicated to all our supporters that read the advisories; took an avalanche class; donated money, time or gear; or sent in observations. Our success is directly related to community support and the Forest Service. Thank you for 28 great seasons. This advisory does not apply to operating ski areas.

Mountain Weather

Winter maintains its edge over spring this morning with 3-4” of new snow throughout the advisory area. Temperatures this morning are teens to low 20s F and wind is westerly at 15-20 mph with gusts of 30-40 mph overnight. Today, temperatures will be high 20s to mid-30s F with west wind at 15-25 mph and mostly cloudy skies. Intermittent snow showers are likely through today and tonight and the mountains will get 3-6” of snow by morning. Clear spring weather is forecast late Monday and Tuesday followed by more active and wet weather later in the week.

Snowpack and Avalanche Discussion

All Regions

A fast, wet storm last night blanketed the advisory area with 3-4” of snow equal to .4-.6” of snow water equivalent (SWE). This storm began as rain and quickly changed to snow. The snowpack is 8-12 feet deep and generally stable below the recent snow, and deeper avalanches are not likely. Today, dry or wet loose avalanches of new snow are possible, and fresh wind slabs could be easy to trigger.

Above freezing temperatures yesterday, and brief sunshine in some locations, created a wet snow surface that probably froze as the storm moved in last night. Today’s new snow may slide easily on the firm, old snow surface. Assess how new snow bonds to old snow on small test slopes before riding in bigger terrain. Anticipate wet loose avalanches if temperatures get above freezing or if the sun shines.

Moderate westerly wind drifted the new snow into slabs 6-12” thick. These slabs are mostly confined to ridgelines, but could be easy to trigger. Avoid steep, wind loaded slopes if you see cracking of fresh drifts on test slopes or lower angle terrain. Even small slides are extremely hazardous in more consequential terrain. Evaluate snow and terrain carefully today. Avoid freshly wind loaded slopes, and avoid steep slopes if new snow easily slides.

New snow and moderate wind make fresh wind slabs likely and loose snow avalanches possible today. Avalanche danger is rated CONSIDERABLE on wind loaded slopes and MODERATE on non-wind loaded slopes.

The mountains got 2-3 feet of snow over the last week. Though not likely, avalanches can break within this recent snow where the snow was less affected by above freezing temperatures yesterday (e.g., higher elevation, shady slopes). On Thursday, Eric and his partner remotely triggered an avalanche on the Throne in the northern Bridger Range. It broke above an ice crust 18-20” deep, 200’ wide and ran 5-600’ vertical (video, photo). Dig a couple feet to assess the recent snow before committing to steeper terrain.

If you get out and have any avalanche or snowpack observations to share, drop a line via our website, email (mtavalanche@gmail.com), phone (406-587-6984), or Instagram (#gnfacobs).

Info and Announcements

We will issue weather and snowpack updates on Monday and Friday mornings for most of April.

Hyalite Canyon road is closed to vehicles and reopens May 16th.

Send us your observations on Instagram! #gnfacobs

Posting your snowpack and avalanche observations on Instagram (#gnfacobs) is a great way to share information with us and everyone else this spring.

The Last Word

Sledders, mark your calendar for May 19, the 2nd Annual Sled Fest in Cooke City. It’s a fundraiser for the Friends of the Avalanche Center and there will be a DJ, raffle prizes and BBQ on the mountain.

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